JP-A-2000-6687 discloses a safety operation system. When a driver operates an apparatus, e.g., vehicle navigation device, in a vehicle, the system extracts an operation object, e.g., finger of the driver or touch pen, by using an image processing. The extracted operation object is displayed on a display screen, and overlaps with other images on the display screen. Thus, the driver can safely operate the apparatus, because the driver can see the operation object on the display screen in front of the driver.
JP-A-6-84081 discloses a method of extracting the operation object using a chromakey image. In the method, a color gain of a video signal is variable. After the color gain of the video signal is controlled, the chromakey image having a predetermined color is extracted. Then, the extracted chromakey image is determined to have a predetermined shape or not. When the extracted chromakey image has the predetermined shape, the operation object can be extracted.
However, outside light passing through a window of the vehicle may change its brightness and color. Therefore, the operation object may not stably be detected, because the brightness and the color in the vehicle are changed by direct sunlight, shadow, or tunnel lighting, when a certain brightness and a certain color are used in the method. Further, in order to deal with an illuminance variation of outside light, a camera having a wide sensitivity range is used, or lens aperture is controlled in a wide range. Thus, cost of the safety operation system may be increased.